Stroke drug trials are often inconclusive. Opposing results are commonly reported due to the multitude of experimental animal models. Most important in this discussion is the influence of blood pressure, temperature, and species on the outcome of stroke drug trials. However, even with strict control of physiological variables, stroke volumes vary experimentally. Often large numbers of experimental animals are required for a conclusive outcome study. We investigated the possibility of using the change in stroke volume observed acutely (1- 8 hrs) on diffusion-weighted MRIs as a basis for stroke drug trials.